14.call apply

call apply 都是为了改变this得指向

 function Compute() {
            this.plus = function (a, b) {
                console.log(a + b);
            }
            this.minus = function* (a, b) {
                console.log(a - b);
            }
 }
  function FullComputed() {
            Compute.apply(this)
            this.mul = function (a, b) {
                console.log(a * b);
            }
            this.div = function (a, b) {
                console.log(a / b);
            }
}
let computed = new FullComputed()
computed.plus(1, 2)